The present invention relates to the art of diagnostic imaging. It finds particular application in conjunction with a separate and combined multi-modality diagnostic imaging system, and more particularly, a separate and combined computed tomographic/nuclear medicine (CT/NUC) diagnostic imaging system. It should be appreciated, however, that the present invention may find application with imaging modalities other than computed tomography (CT) and/or nuclear medicine (NUC).
Nuclear medicine imaging, such as single photon emission computed tomography (SPECT), is used to study radionuclide distribution in subjects. Typically, one or more radiopharmaceuticals are injected into a subject. The radiopharmaceuticals are commonly injected into the subject's blood stream for imaging the circulatory system or for imaging specific organs which absorb the injected radiopharmaceuticals. One or more gamma or scintillation camera heads are placed closely adjacent to a surface of the subject to monitor and record emitted radiation.
In single photon-emission computed tomography, the camera head(s) is rotated slowly or indexed around the subject to monitor the emitted radiation from a plurality of directions. The radiation data from the multiplicity of directions monitored over several minutes, e.g. 10-20 minutes, is reconstructed into a three dimensional image representation of the radiopharmaceutical distribution within the subject.
In computed tomographic (CT) diagnostic imaging, a thin fan-shaped beam of radiation is projected from an x-ray source through a region of interest. The radiation source is rotated rapidly about the region of interest such that the same thin slice of the region of interest is irradiated from a multiplicity of directions spanning 360.degree.. For a volumetric image representation, the source rotates at speeds on the order of 1 sec/revolution or less while the patient is moved longitudinally to irradiate the patient along a spiral path.
Typically, computed tomographic (CT) imaging systems and nuclear medicine imaging systems are located in separate imaging suites with no physical and/or functional connections therebetween. The diagnostic images that result from the respective imaging studies can be viewed concurrently on adjoining screens for diagnostic purposes. However, the value of these image combinations and comparisons is compromised by having been obtained in separate study episodes. These separate study episodes are performed at different locations between which the patient typically walks. Repositioning the patient in the same position is imprecise. The episodes are usually separated by significant Lime intervals (days or even weeks) after which significant functional and anatomical changes can occur in addition to the repositioning problem. These separate study episodes are also performed by different medical personnel which distracts from the comparative value of the separate images.
U.S. Pat. No. 5,391,877 describes a dedicated combined diagnostic, imaging device that fuses together data obtained by a computed tomographic (CT) scanner and a single photon emission computed tomographic scanner (SPECT) to yield a color shaded relief image. The combined diagnostic imaging device includes combined gantries supporting both of the CT and SPECT scanners, a computer, a printer, and a table top that passes through both gantries while holding a patient in a fixed position.
However, the combined diagnostic imaging device described in the '877 patent requires an inefficient use of dedicated imaging hardware and patient care personnel. That is, the CT detectors and CT gantry sit idle most of the time waiting for the temporally longer nuclear study to complete.
Accordingly, it has been considered desirable to develop a new and improved separate and combined multi-modality diagnostic imaging system which meets the above-stated needs and overcomes the foregoing difficulties and others while providing better and more advantageous results.